Transpiler vs Polyfills

#javascript #polyfills #transpiller #es6

In modern web development, maintaining compatiablity across different browsers and environments is a crucial challenge. Two important tools that help developers overcome this issue are transpilers and polyfills. Both serve the purpose of making code work across different platforms, they operate in distinct ways.

What is Transpilers

A transpiler is a tool that converts code written in one language ot syntax to another language or syntax. Specially, in the context of Javascript, transpilers convert modern Javascript (ES6+) into older versions of Javascript (like ES5) that can be understood by older browsers on environments.

key points:

- Syntax-Level Conversion: A transpiler converts code by transforming newer syntax and features( e.g. let,const, arrow functions) into equivalent constructs in older version. It ensures the same code runs across different environments.

E.g. Babel - Converts modern ES6+ code into ES5.
TypeScript Compiler - Converts Typescript into plain JavaScript.

ES6 code

let greet = () => console.log("Hello World!");

A transpiler would convert it to ES5, looks like :

var greet = function () {
console.log("Hello World!");

What is Polyfills?

A Polyfill is a piece of code, that provides missing functionality in older browsers or environments.It "fills in" the gaps where. a certain feature is not natively supported.

key points:

-Feature Level Emulation: Unlike a transpiler, which transforms code syntax, a polyfill implements missing features.

Polyfills are added at runtime and do not modify the source code.

E.g - includes polyfills

For browsers that don't support the Array.prototype.includes method, a polyfill can be implemented like this:

if(!Array.prototype.includes) {
Array.prototype.includes = 
  function(searchElement) {
    return this.indexOf(searchElement) !== -1
  }
}

Key Difference

By using transpiler, we can ensure the code is compatible with older environments, while polyfills allow to add missing functionality. Together they allow developers to write modern, efficient code without worrying about breaking support for older platforms.